With the continuous development of semiconductor technology, the size of semiconductor devices has become smaller and smaller. Thus, more defects may occur in CMOS transistors formed on a bulk silicon semiconductor substrate. Further, certain related effects, such as short channel effects, channel punch through effects, or reduction of gate control ability effects, etc., may become more severe using the bulk silicon semiconductor substrate. In order to improve the performance of the semiconductor devices formed on the bulk silicon semiconductor substrate, various device structures have been developed. Such device structures include fully depleted silicon on insulator (FDSOI) devices, fin-field effect transistors (FinFETs), omega gate devices, or gate-all-around nanowire devices, etc.
As multiple gate devices, FinFETs have relatively high gate control abilities. Further, the doping concentration of the channel regions of existing FinFETs is usually relatively low. The low doping concentration may aid to obtain relatively stable threshold voltages. However, comparing with the bulk silicon CMOS transistors, the fabrication process of FinFETs may be more complex; and the production cost may be much higher.
Further, in order to improve the performance of the FinFETs, different materials are often used as the fin materials according to the types of carriers of the FinFETs. However, comparing with the silicon substrate, the production cost of FinFETs formed by using semiconductor materials other than silicon may be relatively high.
Therefore, new device structures and methods may need to be developed to improve the performance of the FinFETs without increasing the production cost. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.